1. Field
The present disclosure relates generally to identifying the position of an aircraft and reporting the position of the aircraft from the aircraft to a location off of the aircraft. More particularly, the present disclosure relates to a method and apparatus for verifying that position information identifying the position of an aircraft that is received from the aircraft is trustworthy, so that appropriate action may be taken using the position information from the aircraft.
2. Background
Aircraft may include various systems for determining the position of the aircraft and for reporting the position of the aircraft from the aircraft to a location off of the aircraft. The aircraft position reported from the aircraft may be used to take appropriate actions under various conditions.
For example, without limitation, many aircraft carry distress radio beacons. Distress radio beacons may be known as emergency beacons or by other names. For example, without limitation, many commercial passenger aircraft and other aircraft may carry a distress radio beacon known as an emergency locator transmitter, or ELT.
An emergency locator transmitter on an aircraft is intended to aid in locating the aircraft after a crash. An emergency locator transmitter on an aircraft may be manually or automatically activated to send out a distress signal when the aircraft is in distress. For example, without limitation, an emergency locator transmitter may be activated to transmit a distress signal automatically upon immersion in water or when another condition indicating that the aircraft is in distress is detected.
A search and rescue system may detect a distress signal generated by an emergency locator transmitter or other distress radio beacon on an aircraft and respond in an appropriate manner. For example, COSPAS-SARSAT is an international humanitarian search and rescue system for locating and responding to aircraft, ships, or individuals in distress. The COSPAS-SARSAT system includes a network of satellites, ground stations, mission control centers, and rescue coordination centers.
COSPAS-SARSAT uses satellites to detect distress signal transmissions from emergency locator transmitters on aircraft. The signal from an emergency locator transmitter on an aircraft is received by a satellite in the COSPAS-SARSAT system and relayed to the nearest available ground station. The ground station, called a Local User Terminal, processes the signal and determines the position from which it originated. The primary means for determining the position of the transmission from the emergency locator transmitter is using satellite orbit information and signal Doppler measurements. In some cases, an emergency locator transmitter may be configured to determine its location using a satellite navigation system receiver that is either integrated into the emergency locator transmitter or fed by a satellite navigation system receiver that is not part of the emergency locator transmitter.
Information identifying the position of the emergency locator transmitter is transmitted from the ground station to a mission control center where it is joined with identification data and other information associated with the emergency locator transmitter. The mission control center then transmits an alert message to an appropriate rescue coordination center based on the determined geographic location of the detected transmission from the emergency locator transmitter and other available information.
Current emergency locator transmitters may have several limitations. For example, position information provided by current emergency locator transmitters may not be sufficiently accurate or provided in a sufficiently reliable manner to locate an aircraft in distress effectively. The majority of currently fielded emergency locator transmitters do not provide position information directly. The location of the emergency locator transmitter is determined by radio frequency direction finding or multilateration through satellite links. This process may take an undesirably long time and may not be sufficiently reliable.
Accordingly, it would be beneficial to have a method and apparatus that take into account one or more of the issues discussed above, as well as possible other issues.